1. Field of the Invention
The present invention relates to an electromagnetic wave detecting element. In particular, the present invention relates to an electromagnetic wave detecting element that uses a TFT (thin-film transistor) active matrix substrate that detects an image and at which sensor portions are provided in correspondence with respective intersection portions of plural scan lines and plural signal lines that are disposed so as to intersect one another.
2. Description of the Related Art
Radiation image detection devices such as FPDs (flat panel detectors), in which an X-ray sensitive layer is disposed on a TFT (thin film transistor) active matrix substrate and that can convert X-ray information directly into digital data, and the like have been put into practice in recent years. As compared with a conventional imaging plate, an image can be confirmed immediately at an FPD. Further, the FPD has the advantage that video images as well can be confirmed. Therefore, the popularization of FPDs has advanced rapidly.
Various types of radiation image detection devices are proposed. For example, there is a direct-conversion-type radiation image detection device that converts radiation directly into charges and accumulates the charges. Moreover, there is an indirect-conversion-type radiation image detection device that once converts radiation into light at a scintillator of CsI:Tl, GOS (Gd2O2S:Tb), or the like, and, at semiconductor layer, converts the converted light into charges and accumulates the charges.
At the electromagnetic wave detecting element, sensor portions, that generate charges due to electromagnetic waves that are the object of detection being irradiated, are provided on a TFT active matrix substrate at which plural scan lines and plural signal lines are disposed so as to intersect one another, and TFT switching elements are provided at the respective intersection portions of the scan lines and the signal lines. However, the sensor portions must be provided so as to avoid the TFT switching element portions.
Thus, U.S. Pat. No. 5,619,033 discloses a structure in which flattening (leveling) films (interlayer insulating films) are provided above and below the sensor portions. In the technique of U.S. Pat. No. 5,619,033, the scan lines, the signal lines and the TFT switching elements are covered by a lower layer flattening film such that the surfaces thereof are flattened (leveled), and sensor portions are provided on this lower layer flattening film. Due thereto, there is no need for the sensor portions to be disposed to avoid the TFT switching element portions, and the surface areas of the sensor portions can be made larger. Further, by covering the sensor portions with an upper layer flattening film and filling in the gaps between the respective sensor portions, edge defects at the time of upper layer metal patterning can be prevented.
However, in a case of providing flattening films above and beneath the sensor portions by using the technique disclosed in U.S. Pat. No. 5,619,033, it becomes easy for cracking of the peripheral portion of the substrate and breakage of the lead-out wires to arise.
For example, as shown in FIG. 9, a substrate 1′, at which the scan lines, the signal lines and the TFT switching elements are provided, is covered by a first flattening film 12′. Sensor portions 103′ are provided on the first flattening film 12′, and a second flattening film 18′ is provided on the first flattening film 12′ so as to cover the sensor portions 103′. In this case, because there are the two layers of flattening films, i.e., the first flattening film 12′ and the second flattening film 18′, there is an increased number of steps (number of stepped levels due to layered films) at the peripheral portion of the substrate 1′. Further, at the time of patterning the second flattening film 18′ on the first flattening film 12′, it is easy for residue to remain on the first flattening film 12′ at the edge portions of the second flattening film 18′. Such steps and residue may cause cracking of the upper layer films that starts at the steps or the residue, or may cause breakage of the lead-out wires.